The present invention relates to machines (e.g., motors) that include rotational members, more particularly to methods and apparatuses for imposing torque loading upon a rotational member for purposes of conducting testing (such as involving vibration, e.g., acoustic vibration) of a machine.
Vibration, such as sound vibration (e.g., that which produces noise), is an important consideration in the operation of various types of machinery. The current methodologies for providing a torque load for vibration testing of machines such as motors are deficient in terms of induced load smoothness, heat generation and vibration generation. The devices conventionally used for motor testing include Prony brakes, water brakes, generator loads, and magnetic rheological devices.
It is desirable that a “quiet load” be used for vibration testing of a “quiet motor” so as to minimize or avoid contribution of vibration by the load to the overall vibration that is being measured with attribution to the motor. When a quiet motor is to be tested (e.g., for an endurance test), it is unsuitable to use a noisy load for testing, as such would represent an abnormal operating condition for the motor. A quiet motor is designed to operate quietly, in a quiet environment, and the introduction of a noisy test component would be incongruous. A “quiet motor,” as the term is used herein, is a motor that is designed to generate a relatively low amount of vibration during operation of the motor. A “quiet load,” as the term is used herein, is an induced load that generates as little vibration as possible at all frequencies (or all significant frequencies) during induction of the load with respect to the motor during testing (e.g., vibration testing) of the motor. It is further desirable that the load be able to operate over wide ranges of speed and torque.